Active suppression of imbalance vibration in the magnetically suspended control moment gyro

The magnetically suspended control moment gyro (MSCMG) system is an actuator for attitude control of spacecrafts. It consists of a gimbal and a high-speed rotor suspended by magnetic bearings (MBs). The imbalance vibration due to the high-speed rotor can cause a velocity ripple to the gimbal and be transmitted to the spacecraft to decrease its attitude control precision. To suppress the imbalance vibration, this paper introduces an active control method in both the MBs and gimbal systems. Firstly, the structure and dynamics of the MSCMG system with the MBs and gimbal are described, and the transmission of the imbalance vibration is discussed. Then a notch filter with a phase shift and a feedforward controller are designed to prevent the MB system from generating the imbalance vibration by making the rotor rotate around its inertial axis. To correct the feedforward control errors resulting from power amplifiers, phase and gain compensations are made. Finally, another notch filter with a phase shift is employed to suppress the velocity ripple caused by the residual vibration from the MB system, and a constant-gain Kalman filter is adopted to obtain the best real-time estimate value of the gimbal velocity. Stabilities of the vibration control method and the Kalman filter are analyzed. Simulations and experiments have been performed to validate the proposed control method, which has a short computation time and can be used in many practical applications.